In standard stent delivery systems, the proximal portion of the catheter is manufactured from materials that make it relatively stiff or inflexible, which endows the catheter with adequate pushability. By contrast, the distal portion of the catheter is manufactured to be rather flexible to allow adequate deliverability of the stent through tortuous vessels to the desired target.
In the case of a balloon catheter, the balloon, which is located at the distal portion of the catheter, is delivered in a deflated state, wrapped around the catheter's inner inflation tube and covered by a crimped stent. The balloon distal shoulder may be fused to the catheter's inner inflation tube. The whole catheter is designed to glide on a guide wire, with the catheter tip serving as the leading part of the catheter to, for example, penetrate a lesion, navigate through a curved vessel, or pass through an already deployed stent within the vessel.
The properties of the catheter tip determine to a large extent whether or not the catheter will catch on the rough surface of the vessel, the surface of vessel lesion or obstruction, or the struts of a previously deployed stent.
Current catheter tips of stent delivery systems and on angioplasty balloon systems are made of plastic material and have a tip shape that is aimed to provide deliverability of the catheter through challenging anatomies. Two parameters may be adjusted to improve deliverability. The catheter tip may be designed to have longitudinal flexibility to accommodate tortuous vessels, and/or the tip shape and its radial rigidity may be modified to avoid collapse of the distal edge of the tip and/or kinking of the proximal neck of the catheter tip when obstacles are encountered. Optimizing both parameters simultaneously in a catheter tip is problematic, as longitudinal flexibility requires a very thin or flexible material, while pushability and radial rigidity require a thick or stiff material.
Therefore, there is a need in the art for an endovascular catheter tip that is longitudinally flexible and pushable and has radial rigidity at its distal end—in particular at the distal edge, to optimize deliverability of the catheter.